The classes of secondary plant metabolites include:
- Phenolics
- Alkaloids
- Saponins
- Terpenes
- Lipids
- Carbohydrates
What are secondary metabolites and how are they classified?
Based on the structure of the compounds, the secondary metabolites are classified into five major classes: In plants, these compounds help in protecting them from pathogens and pests, help in pollination, and provide protection against UV damage.
What are the secondary metabolites of nitrogen synthesis in plants?
The nitrogen containing secondary metabolites such as alkaloids are synthesized in plants primarily from amino acids. An overview of the major biosynthetic pathways of secondary metabolites and their interrelationships with primary metabolism in plants is given in Fig. 24.1.
How do secondary metabolites affect plant growth?
Secondary metabolites may also inhibit the growth of competitor plants (allelopathy). Pigments (such as terpenoid carotenes, phenolics, and flavonoids) color flowers and, together with terpene and phenolic odors, attract pollinators.
Are lipids primary or secondary plant metabolites?
Although lipids are considered primary plant metabolites, recent studies revealed pharmacological activities to members of this class of phytochemicals. 6.1. Fixed oils Fixed oils constitute of high molecular aliphatic long-chain fatty acids, such as palmitic, stearic and oleic acids, esterified with glycerol.
What are the classes of secondary metabolites?
There are five main classes of secondary metabolites such as terpenoids and steroids, fatty acid-derived substances and polyketides, alkaloids, nonribosomal polypeptides, and enzyme cofactors [6].
What are secondary metabolites and give four examples?
Secondary metabolites, also called specialised metabolites, toxins, secondary products, or natural products, are organic compounds produced by any lifeform, e.g. bacteria, fungi, animals, or plants, which are not directly involved in the normal growth, development, or reproduction of the organism.
What are the main groups of secondary metabolites of the plant?
The classes of secondary plant metabolites include:Phenolics.Alkaloids.Saponins.Terpenes.Lipids.Carbohydrates.
What are the 4 main groups of primary metabolites in plants?
PSMs are broken into four major groups: Alkaloids, Terpeniods, Phenolics, and Sulfated Amino Acids.
What are secondary metabolites in plants give examples?
Toxins, gibberellins, alkaloids, antibiotics, and biopolymers are examples of secondary metabolites.
Which of the following are secondary metabolites in plants?
Metabolites that are not involved in the growth and development directly are called secondary metabolites. Example: alkaloids, tannins, resins, gums, latex, etc.
What are primary and secondary metabolites in plants give examples?
The primary metabolites include amino acid, lactic acid, vitamins, carbohydrates, lipids, etc. Steroids, alkaloids, essential oils, phenolic, etc. are a few examples of secondary metabolites.
What are the functions of secondary metabolites in plants?
Secondary metabolites serve: (i) as competitive weapons used against other bacteria, fungi, amoebae, plants, insects, and large animals; (ii) as metal transporting agents; (iii) as agents of symbiosis between microbes and plants, nematodes, insects, and higher animals; (iv) as sexual hormones; and (v) as ...
What are secondary metabolites in plants PPT?
Secondary metabolites are organic compounds that are not directly involved in the normal growth, development, or reproduction of an organism. Secondary metabolites are organic compounds that are not directly involved in the normal growth, development, or reproduction of an organism.
How many secondary metabolites are there?
They act as antimicrobials and perform the role of attractants or, conversely, as repellents. Over 50,000 secondary metabolites have been discovered in the plant kingdom. Medicinal herbs and many modern medicines rely on secondary plant metabolites for their actions.
What are primary and secondary metabolic?
Metabolites are intermediate end products of metabolism. Primary metabolites are essential for the proper growth of microorganisms. Secondary metabolites are formed near the stationary phase of growth and are not involved in growth, reproduction and development.
What is the difference between primary and secondary metabolites in plants?
The main difference between primary metabolites and secondary metabolites is that primary metabolites are directly involved in primary growth development and reproduction whereas secondary metabolites are indirectly involved in metabolisms while playing important ecological functions in the body.
What is secondary metabolites and their types?
Types of Secondary Metabolites: Isoprenoids or Terpenes, e.g., rubber, steroids, essential oils, carotenoid pigments. 2. Nitrogen containing compounds, e.g., alkaloids, glucosinolates, glycosides, non-protein amino acids.
What are secondary metabolites Class 11?
Secondary metabolites are organic compounds formed by different organisms that are not directly involved in the organism's development, growth, or reproduction, but are important in ecological and other activities. They are also referred to as “central metabolites”.
What are examples of metabolites?
Examples of primary metabolites are ethanol, glutamic acid, aspartic acid, 5′ guanylic acid, acetic acid, lactic acid, glycerol, etc. Examples of secondary metabolites are pigments, resins, terpenes, ergot, alkaloids, antibiotics, naphthalenes, nucleosides, quinolones, peptides, growth hormones, etc.
What is secondary metabolism Class 12?
Secondary metabolism (also called specialized metabolism) is a term for pathways and small molecule products of metabolism that are not absolutely required for the survival of the organism.
What are the two types of metabolites in plants?
Types of metabolites in plants. Plants have basically two types of metabolites namely Primary metabolites and Secondary metabolites. Primary metabolites are mainly used for photosynthesis, growth, development and respiration of plants. Secondary metabolites accumulate in plants and response as a defence mechanism of the plants.
What are the three major groups of secondary metabolites?
Secondary metabolites can be divided into three major groups. Flavonoids. Alkaloids. Terpenoids. 1. Flavonoids. Flavonoid: General structure. These are polyphenolic compounds comprise of 15 carbons with two aromatic rings connected by a three-carbon bridge. Subtypes of flavonoids are.
What is a secondary metabolite?
Secondary metabolites or Phytochemicals (Plant chemicals) are the natural products or plants constituents which are responsible for the medicinal properties of plants. There are thousands of secondary metabolites . some plants are classified on the basis of secondary metabolites found in them.
What is the most diverse group of secondary metabolites found in plants?
Terpenoid: General Structure. Terpenoids are the volatile substance which gives plants and flowers its unique fragrance, this is the largest and most diverse group of secondary metabolites found in plants.
What are alkaloids known for?
Alkaloids are well known for their antioxidant, anti-inflammatory and cardioprotective activities.
What are the functions of alkaloids in plants?
The major function of alkaloids in plants. Defence mechanism against bacteria and other microorganisms. Helps in plant metabolisms and catabolisms. Storage and reservoir of nitrogen. As growth regulators in plants. It also helps as a growth stimulator and inhibitors.
How many alkaloids are there in the world?
More than 12,000 alkaloids are known so far. They are bitter in taste and medicinally important. Alkaloids are used in many pharmaceutical companies for the preparation drugs like narcotics, morphine, atropine and stimulants etc. Alkaloids are mainly divided into three categories.
How are secondary metabolites classified?
Secondary metabolites can be classified on the basis of chemical structure (for example, having rings, containing a sugar), composition (containing nitrogen or not), their solubility in various solvents, or the pathway by which they are synthesized ( e.g., phenylpropanoid, which produces tannins). A simple classification includes three main ...
Why do plants have secondary metabolites?
The apparent lack of primary function in the plant, combined with the observation that many secondary metabolites have specific negative impacts on other organisms such as herbivores and pathogens , leads to the hypothesis that they have evolved because of their protective value. Many secondary metabolites are toxic or repellant to herbivores and microbes and help defend plants producing them. Production increases when a plant is attacked by herbivores or pathogens. Some compounds are released into the air when plants are attacked by insects; these compounds attract parasites and predators that kill the herbivores. Recent research is identifying more and more primary roles for these chemicals in plants as signals, antioxidants , and other functions, so "secondary" may not be an accurate description in the future.
What are the mechanisms that affect the growth of a plant?
Most herbivores and plant pathogens possess mechanisms that ameliorate the impacts of plant metabolites, leading to evolutionary associations between particular groups of pests and plants. Some herbivores (for example, the monarch butterfly) can store (sequester) plant toxins and gain protection against their enemies. Secondary metabolites may also inhibit the growth of competitor plants (allelopathy). Pigments (such as terpenoid carotenes, phenolics, and flavonoids) color flowers and, together with terpene and phenolic odors, attract pollinators.
Why are secondary chemicals important?
Secondary chemicals are important in plant use by humans. Most pharmaceuticals are based on plant chemical structures, and secondary metabolites are widely used for recreation and stimulation (the alkaloids nicotine and cocaine; the terpene cannabinol). The study of such plant use is called ethnopharmacology. Psychoactive plant chemicals are central to some religions, and flavors of secondary compounds shape our food preferences. The characteristic flavors and aroma of cabbage and relatives are caused by
What are the chemicals that protect plants from pests?
nitrogen-and sulfur-containing chemicals, glucosinolates, which protect these plants from many enemies. The astringency of wine and chocolate derives from tannins. The use of spices and other seasonings developed from their combined uses as preservatives (since they are antibiotic) and flavorings.
What are the compounds that are considered secondary metabolites?
These compounds are extremely numerous and chemically diverse in nature and are called as secondary metabolites or secondary plant products or natural products and include such well known substances as alkaloids, terpenes, (including steroids and rubber), tannins, flavonoids etc.
What are secondary metabolites?
Although previously unknown, the role of secondary metabolites in plant defenses against herbivores and pathogens is being increasingly recognised now. Some of these are also known to attract animals for pollination and seed dispersal and as agents of plant-plant competition.
What are the organic compounds found in plants?
The organic compounds such as carbohydrates, proteins, fats, membrane lipids, nucleic acids, chlorophylls and hemes are found throughout the plant kingdom and are central to the metabolism of plants. These compounds are known as primary metabolites.
What is secondary plant product?
ADVERTISEMENTS: According to Street and Cockburn (1972) “secondary plant products are compounds which have not so far been shown to be involved in primary metabolism; as far as their functions can at present be assessed they are accessory rather than central to the physiology of the plants in which they occur”.
Where are alkaloids synthesized?
The nitrogen containing secondary metabolites such as alkaloids are synthesized in plants primarily from amino acids. An overview of the major biosynthetic pathways of secondary metabolites and their interrelationships with primary metabolism in plants is given in Fig. 24.1.
Do plants have a direct function in growth?
Apart from these substances, many plants particularly those of certain genera and families synthesize a number of organic compounds in them which are not in the mainstream of metabolism and appear to have no direct function in growth and development of plants.
What are the primary and secondary metabolites of plants?
On the other hand, secondary plant metabolites are products of subsidiary pathways as the shikimic acid pathway.
What is secondary metabolite?
Secondary plant metabolites are numerous chemical compounds produced by the plant cell through metabolic pathways derived from the primary metabolic pathways. The concept of secondary metabolite was first defined by Albrecht Kossel, Nobel Prize winner for physiology or medicine in 1910 [ 2 ].
What are phenolics in plants?
Phenolics probably constitute the largest group of plant secondary metabolites. They share the presence of one or more phenol groups ( Figure 1) as a common characteristic and range from simple structures with one aromatic ring to highly complex polymeric substances. They are widespread in plants where they contribute significantly to the color, taste and flavor of many herbs, foods and drinks. Some phenolics are valued pharmacologically for their anti-inflammatory activities such as quercetin or antihepatotoxic properties such as silybin. Others exert phytoestrogenic activity as genistein and daidzein, while others are insecticidal as naringenin [ 5 ]. Many of the phenolic molecules are also effective antioxidants and free radical scavengers, especially flavonoids. Phenolics can be classified according to their structure or biosynthetic origin. According to their structures, phenolics can be classified into:
How many carbons are in a terpene?
Terpenes having 25 carbons and five isoprene units are rare relative to the other sizes (the sester- prefix means half to three, i.e. two and a half). An example of a sesterterpenoid is geranyl farnesol isolated from seed oils of Camellia sasanqua (sasanqua) and Camellia japonica (camellia), family Theaceae [ 36 ].
What is the role of metabolites in plants?
Modern chemistry has described the role of primary plant metabolites in basic life functions such as cell division and growth, respiration, storage and reproduction.
How many carbon atoms are in monosaccharides?
Monosaccharides contain from three to nine carbon atoms, although those with five and six carbon atoms (pentoses, C 5 H 10 O 5, and hexoses, C 6 H 12 O 6) are accumulated in plants in greatest quantity. Condensation of monosaccharides results in the other types according to the number of saccharide units involved.
What are the two main categories of phytochemicals?
Generally, the phytochemical constituents of plants fall into two categories based on their role in basic metabolic processes, namely primary and secondary metabolites.
Which pathway provides quinones and xanthones?
The polyacetate pathway provides quinones and xanthones.
What are the alkaloids classified as?
According to this criterion the alkaloids are classified as true alkaloids, protoalkaloids, and pseudoalkaloids57. Pure alkaloids strictly comply with the fundamental characteristics of the alkaloids.
What are phenolic compounds?
phenolic compounds is the number of carbons present in the molecule. According to this criterion, the phenolic compounds are classified into simple phenols, acidic phenols, acetophenones, and phenylacetic acids, hydroxycinnamic acids, coumarins, flavonoids, biflavonyls, benzophenones, xhantones, stilbenes, quinones and betacyanins (Table 2). Lignans, neolignans, tannins, and phlobaphenes also belong to this group. The latter are polymers and have more complex structures34,35. Phenolic compounds are synthesized in plant cells by the shikimic acid pathway or the malonate/acetate pathway (or both, for example, flavonoids)36. The shikimic acid pathway provides the synthesis of phenylalanine and cinnamic acids and their derivatives (simple phenols, phenolic acids, coumarins, lignans, and phenyl propane derivatives)37,38. The polyacetate pathway provides quinones and xanthones. The mixed pathways combine precursors of both the shikimic acid pathway and the polyacetate pathway. This is the case of flavonoids39,40. Phenolic compounds fulfill various functions in plants: they oxidize quickly and act as antioxidants41,42,43, they act as plant growth inhibitors44, seeds accumulate significant amounts of phenols that act as filter so that oxygen does not reach the embryo and inhibit its germination45. Phenols also accumulate on surfaces of leaves, capturing up to 90% of UV radiation46. Phenols confer aromas and colors to the fruits making them appetizing for herbivores, which favors the dispersion of seeds through feces47. Plants compete with each other to preserve their territories, and in this process (allelopathy) the phenols participate48. Plants also defend themselves against the attack of pathogens by synthesizing phytoalexins that are toxic to microorganisms and their presence prevents infections49. Phenols also protect plants by generating bitter flavors or textures that are unpleasant for herbivores50. Alkaloids: alkaloids constitute another large and diverse group of SM that includes molecules isolated primarily from vascular plants51. Plants generally produce a complex mixture of alkaloids, in which a significant constituent dominates51. In a given plant the biosynthetic origin of the alkaloids present is common, even if their structures are slightly different51. Another interesting observation is that the concentration of alkaloids varies considerably from one part to another of the same plant, and even in some parts it may not contain those at all52. Alkaloids are also found in fungi, bacteria, and animals53. They include an atom of nitrogen in their structure, are toxic compounds and respond to common precipitation reactions54,55. Even when there is no uniform classification of alkaloids, several criteria have been used in order to classify them: biosynthetic origin, presence of basic heterocyclic nucleus in the structure, pharmacological properties, and distribution in plant families56. Among these criteria, the biosynthetic origin of the alkaloids has been used quite frequently. According to this criterion the alkaloids are classified as true alkaloids, protoalkaloids, and pseudoalkaloids57. Pure alkaloids strictly comply with the fundamental characteristics of the alkaloids. The majority of the alkaloids found in plants belong to this group. They contain an intracyclic nitrogen, have basic character and are compounds of high reactivity, even in small quantities. In plants, they can be found free, although they predominate as salts. The precursor compounds of the true alkaloids are amino acids (L-ornithine, L-lysine, L-tyrosine, L-tryptophan, L-histidine, and L-arginine). Some pure alkaloids have been derived from anthranilic and nicotinic acids57,58. The protoalcaloides constitute a smaller class in number. In this group, the nitrogen atom is not part of the heterocycle, and they derive from L-thyroid, L-tryptophan, and L-ornithine. They can also be considered aromatic amines55. The pseudoalkaloids contain heterocyclic rings with nitrogen but are not derived from amino acids. They are formed by subsequent incorporation of nitrogen into compounds originally free of this element. To this group belong terpenic alkaloids58. Although the presence of alkaloids is not vital for the plant, there is evidence that indicates the roles that these substances play in vegetables. As for the functions they fulfill, at first, they were considered waste products of nitrogen metabolism, nitrogen reservoirs in the plant, and were even mentioned as growth regulators. Today it is accepted that the role they play is to defend the plant against insects and herbivores due to its toxicity and deterrent capacity. While some serve to protect the plant from predators or microorganisms (toxic or repellent substances), others do so to compete with other plant species in a given habitat (allelopathic substances)59,60. Alkaloids have remarkable physiological properties and toxicological that are exerted primarily on the nervous system central, with predominance in some of its levels (Table 3). For these reasons, they can be used as drugs. Prolonged use of any of these compounds produced in man accustoming, which constitute true drug addictions, with physical and psychic dependence and an increase in the tolerance 57,59. To date, around 15,000 alkaloids have been isolated from plants. If it is considered to have been examined less than 25% of the upper plant species of the planet, it is clear that there is still Table 1. Classes of terpenes according to the number of isoprene units.
What is the function of SM in plants?
The compounds derived from secondary metabolism in plants are called secondary metabolites (SM)1. The SM of the plants constitute a large and varied group of organic compounds that are synthesized in small quantities; they have no direct function in essential processes such as photosyn thesis, respiration, solute transport, protein synthesis, nutrient assimilation, and the differentiation or formation of carbohydrates, proteins, and lipids. They appear in plants as a result of chemical conversions and even when many of their functions are unknown, it is believed that SM are related to the defense of the plant against predators and pathogens, they also act as allelopathic agents that influence growth, survival, and reproduction of other plants, attract seed pollinators and serve to face adaptation to sudden changes in temperature, humidity, light intensity and drought2,3,4. The SM of the plants have a differential distribution between taxonomic groups in the Kingdom of the plants, and therefore they are useful for Systematic Botany5. The study of biological functions and the structure of SM are of great importance because from this knowledge, it has been possible to use them in different industries. Many SM are used as aromas, resins, gums, flavor enhancers, as insecticides and herbicides6,7,8,9,10. On the other hand, the majority of SM have found utility in the pharmaceutical industry, given a large number of pharmacological activities that are known about them11. This article summarizes the main classes of SM in plants, some techniques for their extraction from natural sources and phytochemical screening, as well as the main pharmacological activities described for fundamental classes of SM. Classes of SM in plants Several criteria have been considered for the classification of SM: chemical structure (presence of rings or sugars), composition (containing nitrogen or not), their solubility in organic solvents or water, and the biosynthetic pathway. Of them, the most common criterion used for grouping the SM in plants has been the biosynthetic pathway. According to
What are the three groups of SM?
this, the SM in plants can be divided into three large groups: terpenes, phenolic compounds, and alkaloids12. Terpenes: they constitute the largest group of SM in plants to which more than 40,000 different molecules are allocated12.
What are terpenes in plants?
Many plants contain terpenes in their flowers and fruits as mixtures of volatile compounds with specific odors ; among them, we can mention lemon, mint, eucalyptus, ginger, and great basil24. Terpenes have several biological functions and participate in both the primary metabolism and the secondary metabolism of plants.
Why do monoterpenes interact with phospholipids?
It is also known that monoterpenes can interact with the phospholipids of cell membranes of many microorganisms due to their lipophilic nature. As a result, the ordered structure of the membranes is interrupted, thus causing cell lysis103,104. The antioxidant activity has also been studied from plant extracts.
Introduction
Types of Metabolites in Plants
- Plants have basically two types of metabolites namely Primary metabolites and Secondary metabolites. Primary metabolites are mainly used for photosynthesis, growth, development, and respiration of plants. Secondary metabolites accumulate in plants and respond as a defense mechanism of the plants.
What Is A Secondary Metabolite?
- Secondary metabolites or Phytochemicals (Plant chemicals) are the natural products or plants constituents which are responsible for the medicinal properties of plants. There are thousands of secondary metabolites. some plants are classified on the basis of secondary metabolites found in them (1).
Types of Secondary Metabolites and Their Medicinal Properties
- Three major groups of secondary metabolites
1. Flavonoids 2. Alkaloids 3. Terpenoids
Flavonoids
- These are polyphenolic compounds comprised of 15 carbons with two aromatic rings connected by a three-carbon bridge. Subtypes of flavonoids are (7). 1. Flavonol:Most widely distributed flavonoid. Examples are myricetin, quercetin, isorhamnetin, kaempferol. 2. Flavone:Mainly found in herbs like parsley and celery etc. The structure is almost similar to flavonols. Examples are lut…
Alkaloids
- In simple words, alkaloids are a group of chemical compounds having alkaline nature and heterocyclic nitrogen-containing basic compounds of plants (2). These are bi, tri, and tetracyclic derivatives of molecule quinolizidine. So far more than 12,000 alkaloids are discovered. They are bitter in taste and medicinally important. Alkaloids are used in many pharmaceutical companies …
Terpenoids
- Terpenoids are the volatile substance that gives plants and flowers their unique fragrance, this is the largest and most diverse group of secondary metabolites found in plants. Therefore terpenoids are hydrocarbons of plant origin having (C5H8(n as well as oxygenated, hydrogenated, and dehydrogenated derivatives (5). Classification of terpenoids is mainly dependent upon the n…